Multi-cylinder pumps used for pumping heavy flowable materials such as sludge, slurry or concrete are extremely popular in various fields. Concrete pumps are usually mounted on a suitable vehicle, such as a truck or a trailer, and driven on the construction site to carry out the concrete pouring operation. Slurry and sludge pumps are normally stationary and in most instances, they are used in sludge plants.
These types of pumps include a pump body with a plurality of cylinder bores receiving therein reciprocating pistons which are hydraulically actuated. An oscillating valve conduit moves across the deck surface of the pump body between two operative positions, in which the inlet port of the valve conduit is in register with a respective cylinder whose piston is on the discharge stroke.
The fluids usually pumped by this type of equipment are very abrasive and cause extensive wear between the deck surface of the pump body and the valve conduit which is in sliding contact therewith. As a result, sealing problems arise between the pump body and the valve conduit which may considerably degrade the performance of the pump. In order to prevent or at least reduce leakage between these two components of the pump, it has been suggested by the past to provide a tensioning mechanism which urges in sealing engagement the valve conduit against the pump body. Such tensioning systems are mechanically simple however, they require periodic adjustments to compensate for wear of the deck surface. In addition, these adjustments, normally to be performed immediately before the pump start-up procedure, are delicate and require qualified and experienced personnel.